It is known that an organic polymer containing at least one reactive silicon group in the molecule has an interesting property such that even at room temperature the organic polymer yields a rubber-like cured substance through cross-linking based on the formation of a siloxane bond involving the hydrolysis reaction and the like of the reactive silicon group caused by moisture and the like.
Among these reactive silicon group-containing polymers, polyoxyalkylene based polymers and polyisobutylene based polymers, which are disclosed in Japanese Patent Laid-Open Nos. 52-73998, 5-125272, 3-72527, 63-6003, 63-6041, 1-38407 and 8-231758, and the like, have already been industrially produced to be widely used in applications to sealants, adhesives, coating materials and the like.
When resins for use in adhesives used as adhesives for interior panels, adhesives for external panels, adhesives for tiling, adhesives for stone tiling, adhesives for finishing walls and adhesives for vehicle panels and the like are poor in recovery properties and creep resistance, the adhesive layers are distorted with time due to the weights of the adherends and external stress to displace panels, tiles and stone pieces as the case may be. Additionally, when adhesives for finishing ceilings and adhesives for finishing floors are poor in recovery properties and creep resistance, the adhesive layers are distorted with time to form irregularities on the ceiling surfaces and floor surfaces as the case may be. Moreover, adhesives for assembling electric, electronic and precision instruments are poor in recovery properties and creep resistance, the adhesive layers are distorted with time to lead to performance degradation of these instruments as the case may be. Accordingly, the compositions to be used in these adhesives are required to be excellent in recovery properties and creep resistance.
Sealants are generally used for the purpose of imparting water tightness and air tightness by filling these materials in the joints and gaps between various members. Accordingly, because the property to follow over a long period the portions to which these adhesives are used is extremely important, the physical properties of the cured substances of these adhesives are required to be high both in elongation and in strength, and to be excellent both in recovery properties and in durability.
Particularly, excellent recovery properties and durability are required for compositions to be used for sealants for working joints in buildings with large joint variation (cap pieces, periphery of window glass, periphery of window frame/window sash, curtain wall, various exterior panels), sealants for direct glazing, sealants for double glazing, sealants for the SSG technique and the like.
The curable compositions containing these reactive silicon group-containing organic polymers are cured by use of silanol condensation catalysts; usually organotin based catalysts having carbon-tin bonds such as dibutyltin bis(acetylacetonate) are widely used. However, there is a drawback such that the use of organotin catalysts degrades the recovery properties and the creep resistance of curable compositions.
On the other hand, as described in Japanese Patent Laid-Open No. 55-9669, Japanese Patent No. 3062626, and Japanese Patent Laid-Open Nos. 6-322251 and 2000-345054, divalent tin carboxylates can also be used as silanol condensation catalysts. The use of these divalent tin carboxylates yields cured substances improved in recovery ratio and creep resistance. The use of divalent tin carboxylates in combination with carboxylic acids can improve the curability.
However, even by use of the catalysts using divalent tin carboxylates described in the above described publications in combination with carboxylic acids, sometimes no practical curability has been provided.
On the other hand, when a one-component curable composition is prepared by use of a divalent tin catalyst, there has been a problem that the curability is found to be degraded after storage. Japanese Patent Laid-Open No. 2000-345054 discloses a technique which does not cause the curing retardation by virtue of using a non-phthalate based plasticizer even when a divalent tin catalyst is used.
Additionally, Japanese Patent Laid-Open No. 11-116686 describes a technique to decrease the stress while a high recovery ratio is maintained, by adding an acid and an amine each in a content larger than the equimolecular amount in relation to a tin curing catalyst.
Additionally, in these years it has been pointed out that organotin compounds exert heavy load to the environment, and accordingly, catalysts more free from safety problems are required. Further, from the viewpoint of the environmental protection, catalyst systems containing no metals have been required.
Among such catalysts containing no metals, there is a catalytic system in which a carboxylic acid and an amine compound are simultaneously used, as described in Japanese Patent Laid-Open No. 11-116686. However, this catalytic system is lower in activity than the above described metal catalysts, and thus this catalytic system alone has hardly been able to yield practical curability.
Additionally, Japanese Patent Laid-Open No. 2001-342363 discloses a catalytic system in which a carboxylic acid having a specific structure and a bismuth carboxylate having a specific structure are used simultaneously; however, it has been found that when a curable composition concerned is used as an adhesive with an adherend substrate made of anode oxidized aluminum or stainless steel plate, satisfactory adhesion is not obtained in such a way peeling occurs at the interface between the substrate and the adhesive.